1. Field of the Invention
The invention pertains to a process for preparing an isotropic, spinnable solution 94-100 wt. % of which is composed of the following constituents:
cellulose, PA1 phosphoric acid and/or its anhydrides, and PA1 water,
by dissolving cellulose in a phosphoric acid-containing solvent.
2. Descriscption of Related Art
Such a process is known from GB patent publication 263 810, which describes the dissolution of linters cellulose in 85-90% H.sub.3 PO.sub.4. The dissolution of cellulose can be facilitated by adding other reagents, such as glacial acetic acid and ethanol or homologues thereof. The overall time needed to obtain a homogeneous solution amounts to several hours. The solution can be used, e.g., for spinning artificial silk.
The process is also known from SU 1348396 and SU 1397456. In these publications various examples are provided of the dissolution of cellulose in 80-85% H.sub.3 PO.sub.4. These publications show that the dissolving process takes up to several hours (or a multiple thereof) and that during the process there may be a substantial decrease of the degree of polymerization (DP) of the cellulose. The solutions can be used to make fibres or films.